1The effectiveness of intraoral bone block graft in bone augmentationPhetsamone Thanakone1*, Prisana Pripatnanont2#, Narit Leepong2

1Master student in Oral and Maxillofacial Surgery program, Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Prince of Songkla University2, Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Prince of Songkla University, Hatyai, Songkhla, Thailand 90110*p.thanakone@yahoo.com, #prisana.p@psu.ac.th

AbstractThis study aimed to evaluate the efficacy of autogenous bone block in maintaining

bonydimension after ridge augmentation in an edentulous area. Thirteen patients with 36 tooth-sites were included in the study. There were 18 sites in the maxilla and 18 sites in the mandible. Donor sites comprised of 11 sites from the anterior ramus, 8 sites from the symphysis, 13 sites from the anterior iliac crest and 4 sites from the guided bone regeneration (GBR) with bone substitutes. Evaluation had been done by using cone beam computed tomography (CT) at immediate and 4 months postoperatively. Bone biopsy had been done before implantation, micro CT had been analyzed. Results from cone beam CT measurements showed that theaverage width gained immediately fromthe iliac (4.64±1.74 mm) was highest, then the GBR(4.29±1.24 mm), the ramus(3.31±1.41mm) and the symphysis (2.09±1.71mm)respectively. The immediate width gain from the iliac was statistically significant difference from the symphysis (p<0.05). The average final width gained of all groups were less than immediate width gained and the average width reduction from the symphysis was highest (-1.21±1.48 mm), then the ramus(-0.71±0.66 mm), theiliac (-0.42±2.23 mm)and the GBR (-0.15±0.40 mm)respectively. The ridge height reduction was also maximum in the iliac group (-0.99±1.45 mm), then the symphysis (-0.83±0.72 mm), theramus (-0.78±0.69 mm), and the GBR (-0.08±0.23 mm) respectively. Micro CT showedno difference in the percentages of bone volume fraction (%BV/TV) from the ramus(84.52±8.93%)and the symphysis(82.78±8.11%). It can be concluded that the iliac bone graft gained more bone width and height than other sources of the bone, bone remodeling of either sources were not difference.

Keywords: autogenousbone, bone augmentation, bone block graft,boneremodeling, micro-CT

Introduction The goal of pre-implant bone augmentation of the deficient alveolar ridge is

reconstruction of the proper alveolar anatomy through the techniques of socket preservation, horizontal and vertical ridge augmentation, sinus bone grafting, and others. Autogenous bone grafts are considered “the gold standard” due to their compatibility and osteogenic potentials to form the new bone by processes of osteogenesis, osteoinduction, and osteoconduction. A particulate and block autogenous bone has been used for correction of alveolar ridge deficiency. Extraoral site of autogenous block grafts particularly ilium provides a good source of bone material when compares to intra-oral site such as symphysis and retromolar-ramus areas that have limited bone not more than 4 tooth-sites[1].

Although bone graft harvesting from iliac crest give a large amount of bone for reconstruction, it still possesses some drawbacks of donor site morbidity and faster rate of bone resorption than intra oral sites[2, 3]. After bone block graft, timing for implantation

2should be not more than 4 months to maintain volume of graft and wait for bone integration[4, 5].

Several studies have been proposed to achieve alveolar ridge augmentation in partially edentulous patients using bone blocks harvested from the mandible[6]. Mandibular bone either from the ramus or the symphysis is the ideal choice for limited area of surgical field[7-9].

The purpose of this study was to evaluate the effectiveness of alveolar ridge augmentation with bone block grafts harvested from the extra or intraoral sources in partially edentulous patients. The width and height gained after augmentation from cone beam CT were evaluated. The quality of bone formed from various sources was analyzed by using micro CT. Patients and Methods

This study is a prospective clinical study and was conducted at Oral & Maxillofacial Surgery Clinic, Prince of Songkla University, Hatyai, Thailand.

The experimental protocol was approved by the Human Research Ethics Committee, Faculty of Dentistry, Prince of Songkla University. Patients condition ASA I or ASA II classification with these conditions were included in the study, pre implant condition of partial edentulous ridge with alveolar bone defects in a bucco-lingual direction resulting from prior extractionsand require bone graft augmentation, crestal width of ≤4 mm, crestal height of ≥ 10 mm, controlled oral hygiene (fair and good oral hygiene) and absence of any lesions in the oral cavity. Patients were excluded on the basis of these criteria: a smoker, a bruxism, a head and neck irradiated patient, a pregnant woman, a bisphosphonate taken person, a patient who has blood, liver, kidney and autoimmune disease and a poor oral hygiene patient.

Patients satisfying the above criteria were consent and enrolled in the study.The edentulous ridgeswere augmented withautogenous ramus, symphysis, iliac bone block graft, fixed with 1-2 screws, or particulate deproteinized bovine bone (Bio-Oss; Geistlich AG, Wolhusen, Switzerland)covering with resorbable membrane.

1. Procedures1.1 Pre-operative Preparations

Dental model records and standardized dental radiographs including periapical and orthopantomogram were taken. Dental study models were simulated at the augmented area and an individualized acrylic stent was fabricated with perforated line at implant site as a reference line for measuring of dimensional change after ridge augmentation (Fig.1).

Figure 1(A) dental study model (B) dental study models were simulated at the augmented area (C) an individualized acrylic stent was fabricated with perforated line at implant site

A CB

A C

D E F

B

1mm

3mm

5mm

10mm

31.2 Bone harvesting

A bone block was harvested from either the anterior ramus or the symphysis of mandible under local anesthesia with intravenous sedation or the anterior iliac crest under general anesthesia where appropriate. Procedures were done followed the standard procedures and by an experienced oral and maxillofacial surgeon. The bone block was then fixed to the perforated recipient site with 1-2 micro screws. PRF membrane was used to cover the block graft. Flap was closed and suture with 3-0 Vicryl. Antibiotics, analgesic and antiseptic mouth rinse were prescribed as a standard treatment elsewhere. Removable denture was relieved at least 2 mm. out of contact to the grafted tissue. Sutures were removed 10-14 days after the surgery (Fig.2).

Figure 2.Procedure of bone augmentation (A) atrophic ridge at anterior maxilla (B) alveolar ridge deficiency (C) complete decorticate at recipient site (D) the bone block fixed with screw (E) covering with resorbable membrane (E) primary closure

1.3 Clinical Examination & Data Collection Cone beam CT (3D Accuitomo 170, J Morita, Kyoto,Japan) with 90 kvp, 5 mA, 30.8

s, 4x4 cm FOV, 0.08 mm isotropic voxel size at the grafted area was taken within 2 weeks and 4 months postoperative and used for measuring grafted dimension of ridge width at the depth 1mm, 3mm, 5mm and 10mm from the alveolar crest and for measuring the ridge height (Fig.3)

Figure 3. Cone beam CT measurement

4At the stage of implant placement in the intraoral source of graft, a core biopsy of bone

was taken by using a trephine bur with 2-mm in diameter and 6mm in length. Bone biopsy was processed for micro-computed tomography analysis (Fig.4).

Figure4(A) bone core biopsy (B) 3-D structure of bone core from micro CT

2. Micro-computed tomographyTrephined and formalin-fixed bone cores were used for micro-CT analysis (µCT 35,

SCANCO Medical AG, Brüttisellen, Switzerland). The specimens were placed in a sample holder and scanned through 180⁰ at a spatial resolution of 20 µm, which allows for evaluation of the tissue architecture. The image data were reconstructed to create 3-D images for quantitative percent of bone volume analysis.Results

Thirteen patients aged 43.46±13.08 year olds with 36 implant sites participated in the study. There were 18 sites in the maxilla and 18 sites in the mandible. Donor sites comprised of 11 sites from the anterior ramus, 8 sites from the symphysis, 13 sites from the anterior iliac crest and 4 sites from the GBR. Demographic data were presented in Table 1.

Table 1.Demographic data

Source of grafts

No of patient

Gender M F

No ofimplant site

Age Recipient Anterior maxilla

Recipient posterior maxilla

Recipient Anterior mandible

Recipient posterior mandible

Anterior ramus

5 2 3 11 50.8±9.06 4 1 0 6

Symphysis 3 1 2 8 29.33±18.34 1 0 3 4Anterior iliac crest

2 0 2 13 43.50±6.36 6 4 0 3

GBR 3 1 2 4 45.33±8.15 2 0 0 2Total 13 4 9 36 43.46±13.08 13 5 3 15

The morphological ridge width and height from the cone beam CT were presented in Table 2 and Figure 5. Immediate width and height gain represented the width and height gained after augmentation within 2 weeks and final width and height gain representedthe width and height gained after augmentation within 4 months. The immediatewidth gained at

A B

5all levels of measurementsfrom the iliac group was highest (4.64±1.74 mm), then the GBR (4.29±1.24 mm), the ramus(3.31±1.41mm)and the symphysisgroup(2.09±1.71mm). The width gained from the iliac crest was more than the symphysis significantly (p<0.05) at all levels of measurements. The final ridge width gain of the iliac group was still highest (4.21±2.04 mm) but not different from the GBR (4.14±1.33mm) and the ramus (2.91±1.06 mm) but different from the symphysisgroup (0.89±2.54 mm) significantly (p<0.05). There was no difference among each source of bone in the ridge width remodel but the symphysis(-1.21±1.48 mm) underwent most resorption while the GBR(-0.15±0.40 mm) got least resorption. After bone remodeling iliac graft and GBR gained similar bone width at each level and more than intraoral graft from both the ramus and the symphysis (Figure5).Table 2: Immediate, final width and height gain and remodel

Level Ramus Symphysis Iliac GBR

Immediate width gain:1mm3mm5mm10mmAverage

3.31±1.363.74±1.493.87±1.672.29±2.543.31±1.41

2.35±1.742.38±2.672.19±2.211.46±1.742.09±1.71

6.04±1.99*5.57±2.47*4.26±2.07*2.67±2.46*4.64±1.74*

5.19±1.634.35±1.654.23±1.773.41±1.414.29±1.24

Final width gain:1mm3mm5mm10mmAverage

2.29±1.192.79±1.463.08±1.621.33±1.882.91±1.07

1.12±2.530.92±3.311.14±3.240.37±2.360.89±2.54

5.33±1.84*4.81±2.38*4.27±1.87*2.68±2.49*4.21±2.04*

3.51±2.594.50±1.514.27±1.872.96±0.884.14±1.33

Ridge width remodel:1mm3mm5mm10mmAverage

-0.85±0.50-0.34±0.75-0.26±0.37-1.39±1.43-0.71±0.66

-1.23±1.35-1.50±1.78-1.05±1.96-1.09±2.15-1.21±1.48

-0.69±2.88-0.75±3.01-0.25±2.910.01±1.54-0.42±2.23

-0.35±0.38-0.74±2.180.05±0.43-0.45±0.67-0.15±0.40

Immediate height gain Final height gain Ridge height remodel

0.71±0.84-0.05±0.84-0.78±0.69

-1.01±2.55-1.84±2.35-0.83±0.72

4.73±1.75a

3.74±2.14b

-0.99±1.45

1.69±1.381.60±1.27-0.08±0.23

*statistically significant difference from symphysis at p<0.05

astatistically significant difference from other groups at p<0.05

b statistically significant difference from ramus and symphysis at p<0.05

The immediate height gain was also highest in the iliac group (4.73±1.75 mm) and significantly (p<0.05) different from the GBR (1.69±1.38mm), the ramus (0.71±0.84 mm) andthe symphysis group (-1.01±2.55 mm). The final height gain of the iliac group (3.74±2.14

A B

6mm) was still highest and significantly (p<0.05) higher than the ramus (-0.05±0.84mm) and the symphysis group (-1.84±2.35 mm) but not the GBRgroup(1.60±1.27 mm). The ridge height reduction from the iliac group (-0.99±1.45 mm) was reduced most, the GBR group reduced least (-0.08±0.23mm) but not different from other 2 groups (ramus -0.78±0.69mm, symphysis-0.83±0.72mm)

Figure 5(A) Immediate height gain from various sources of graft at each level of measurement , (B) Final width gain

Micro CT was done only in the group of intraoral grafts from ramus and symphysis which showed that the percentages of bone volume fraction (%BV/TV) from ramus (84.52±8.93%)and symphysis(82.78±8.11%) were not different (Table 3). The trabecular thickness (Tb.Thmicron) from ramus (24.02±4.26) and symphysis (23.04±7.94) were also not different.

Table 3: Micro CT evaluation of bone microstructure and bone mineral density from the ramus and the symphysis bone block graft.Donor site Ramus SymphysisBone volume fraction 84.52±8.93 82.78±8.11

Trabecular bone thickness 24.02±4.26 23.04±7.94

Discussion and ConclusionRidgeaugmentation is a common procedure to correct ridge deficiency before

implantation. Cortico-cancellous block harvested from anterior iliac crest give much more volume than intra oral sources, however it undergoes more remodeling and faster resorption[2, 3].The average of ridge width gained in this study from intra oral site was in the range of 2.09 to 3.31mm immediately after augmentation then underwent remodeling and gained final width only 0.89-2.91mm. While the iliac crest gained more width (4.64±1.74 mm) and height (4.73 ±1.75mm) immediately after augmentation and after remodeling the width (4.21±2.04 mm) and height (3.74±2.14 mm) were still higher than augmentation with intra oral graft. This study the iliac site gained maximum width and height while the

7symphysisgained least width and height. Ridge width reduction was maximum in the symphysis group and ridge height reduction was maximum in the iliac group.

However when compared with previous study[10] using mandibular block graft conducted in Italy, lateral augmentation obtained at the time of bone grafting was 5.5±1.3mm, and reduced during healing from graft resorption to 4.3±1.1mm. The other study using ramus block graft gained mean lateral augmentation at the time of augmentation 4.6 ±0.73 mm, then later, at the time of implant insertion, reduced to 4±0.77 mm[11]. Those studies measured direct ridge dimension by using a caliper that a location and method of measurements were not as same as the present study. The width gained from those studies was higher than this present study. Remodeling was 21.8 and 13 %, while our study was 12.12% in the ramus and 41.5 % in the symphysis. The symphysis in this study underwent much resorption because the bone used was thin. The other study [12] used particulate bone fromsymphysis bone together with titanium mesh and compared with mixed particulate bone and deproteinzed bovine bone in Indian patientsand found that the horizontal bone gain was 3.44±0.54 mm and 2.88±0.57 mm, which was more than our study but the method used is different.The dimension of the bone in European patients are larger than Asian people from those three studies, however the dimension in our study was less than others, which may be come from the race,the gender of the patients and the structure of the bone.

If the graft volume is sufficient for the planned reconstruction such as thickness required is less than 3 mm, the mandibular bone is a good choice for graft and the mandibular ramus provided better volume, thickness and less remodeling than the symphysis. In a condition that needs bone thickness more than 3 mm, the iliac source is recommended. Only the iliac and the GBR group provided vertical augmentation and the iliac group (3.74±2.14 mm) gained more height and width than the GBR (1.60±1.27 mm). In case of vertical augmentation, bone block alone might be not enough and could be combined with particulate bone from cortico-cancellous chips or bone substitutes plus GBR. Intraoral graft has limited source of particulate bone and bone thickness, therefore it is suitable for a case that need minor to moderate bone augmentation that limit to the thickness not more than 3 mm and the recipient should have sufficient height.

In conclusion,the iliac bone graft gained more bone width and height than other sources of the bone, bone remodeling of either sources were not difference.

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